1. Field of the Invention
The present invention relates generally to integrated circuit switching power amplifiers, and more specifically, to a pulse-width modulated (PWM) power amplifier in which the output is slope-controlled.
2. Background of the Invention
Pulse-width modulated (PWM) switching power amplifiers, referred to as class-D amplifiers, are currently in widespread use in automotive amplifiers and other audio amplifiers. Class D amplifiers are switching power amplifiers and have higher efficiency than linear amplifiers, making them well suited for personal device, automotive and other battery-driven applications and applications where power dissipation in the form of heat is a problem, such as very high power professional audio applications, as in concert halls.
The output stage of a switching power amplifier is typically a half-bridge, or two half-bridges forming a full bridge switching amplifier. The half-bridges are switched in a non-overlapping fashion, in order to avoid conducting through both transistors in the half-bridge, which would otherwise degrade efficiency and require more robust switching devices or increase their failure rate due to the higher conduction requirements. However, operating a half-bridge in a non-overlapping fashion can cause the body diode of one of the transistors to conduct, causing ringing, generating electromagnetic interference (EMI) and wasting energy. Further, the output slope of the amplifier is uncontrolled during the non-overlap interval, which increases distortion.
Therefore, it would be desirable to provide a switching power amplifier having a controlled slope during switching transitions. It would further be desirable to provide a switching power amplifier that can have h-bridges operated in a non-overlapping manner, without generating ringing or excessive EMI.